Aluminum Alloy, in Particular for a Casting Method, and Method for Producing a Component from Such an Aluminum Alloy

ABSTRACT

An aluminum alloy, in particular for a casting method, where the aluminum alloy includes at least aluminum, magnesium, manganese and copper. The aluminum alloy includes 0.001 to 0.50 wt. % of molybdenum, 0.05 to 0.4.5 wt. % of magnesium, 0.05 to 0.60 wt. % of manganese, up to 1.5 wt. % of iron, 0.25 to 4.00 wt. % of copper and 0.001 to 0.25 wt. % of vanadium.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to an aluminum alloy, in particular for a castingmethod, and to a method for producing a component from such an aluminumalloy.

An aluminum alloy of this type, in particular for a casting method, isalready disclosed for example in DE 10 2011 115 345 A1. In thisinstance, the aluminum alloy comprises at least aluminum (Al), magnesium(Mg), manganese (Mn) and copper (Cu).

The object of the present invention is to produce an aluminum alloy anda method of the type mentioned at the outset such that particularlyadvantageous, in particular mechanical, properties of the component canbe realized.

In order to further develop an aluminum alloy, in particular for acasting method, such that particularly advantageous, in particularmechanical, properties of a component produced from the aluminum alloycan be realized, the invention provides for the aluminum alloy tocomprise between 0.001 weight percent (wt. %) and 0.50 weight percent(wt. %) molybdenum. The aluminum alloy furthermore comprises magnesiumin a range of from 0.05 wt. % to 0.45 wt. %, manganese in a range offrom 0.05 wt. % to 0.60 wt. %, iron up to 1.5 wt. % and copper in arange of from 0.25 wt. % to 4.00 wt. % inclusive and vanadium in a rangeof from 0.001 wt. % to 0.25 wt. %. Preferably, the aluminum alloycomprises at least 0.10 wt. % and less than 0.40 wt. % manganese.

It has been found that, by adjusting the magnesium concentration, inparticular to less than 0.30 wt. %, the proportion of brittleπ-Al8FeMg3Si6 phases can be reduced to the extent that these phases arehardly present and can therefore have no detrimental effect on theductility of the aluminum alloy, or on a component produced from thealuminum alloy. The reduction in the manganese content to less than 0.40wt. % is advantageous insofar that the iron/manganese-containingintermetallic phases Al15(Fe, Mn)3Si2 can be reduced such that thesephases cannot occur in a morphology that is too coarse and block-like.

It has been demonstrated to be additionally particularly advantageousfor the aluminum alloy to comprise molybdenum (Mo) in a range of from0.001 wt. % to 0.50 wt. % inclusive, it being preferable for thealuminum alloy to comprise 0.10 wt. % molybdenum. By adding molybdenumin a targeted manner, for example at a proportion of 0.10 wt. %, arounded molding, including a polygonal morphology, and a finerdistribution of the above-mentioned iron/manganese phases (Fe/Mn phases)can be produced, which leads to a further increase in ductility.Overall, sufficient ductility in the form of elongation at break can berealized as a result, which is then particularly advantageous if thecomponent produced from the aluminum alloy is used in a drivetrain of amotor vehicle. The component can for example be designed as a crankcaseof an internal combustion engine, which is preferably designed as adiesel engine. Alternatively, the component can also be part of aninternal combustion engine of a gasoline engine. A component of thistype, produced from the aluminum alloy, has sufficient strength, inparticular heat resistance, on account of the strength mechanism of thealuminum alloy. Furthermore, the aluminum alloy according to theinvention can be used advantageously for producing, from the aluminumalloy, a cylinder head of the internal combustion engine, which is forexample a reciprocating internal combustion engine, such that a singlealloy for the crankcase and the cylinder head is conceivable. Costs,logistics, energy consumption and CO₂ emissions can thus be reduced inthe foundry and in the recycling process. It is furthermore possible, byartificially ageing the aluminum alloy, to achieve an increase instrength by means of copper-containing and/or magnesium-containingprecipitates in the aluminum matrix.

Using the aluminum alloy according to the invention for producing acomponent, it is possible for the component, in the heat treatment stateT5mod, to have a 0.2% proof stress R_(p0.2) of more than 180megapascals, a tensile strength R_(m) of more than 220 megapascals andan elongation at break A₅ of more than 1 percent at room temperatureand, in the heat treatment state T6red to have a 0.2% proof stressR_(p0.2) of more than 200 megapascals, a tensile strength R_(m) of morethan 230 megapascals and an elongation at break A₅ of more than 1.5percent at room temperature. In the heat treatment state T5mod, at atest temperature of 150° C., it was possible to achieve the followingvalues: R_(p0.2)>170 megapascals, R_(m)>210 megapascals and A₅>1.5percent.

In the heat treatment state T6red, at a test temperature of 150° C., itwas possible to achieve the following values: R_(p0.2)>200 megapascals,R_(m)>220 megapascals and A₅>3 percent.

The invention is based in particular on the following findings: brittleintermetallic phases are suppressed in alloys having a high Fe content(Fe: iron) by means of the low magnesium content, or magnesiumproportion, which leads to an increase in ductility. Copper leads to asignificant increase in strength by means of artificial ageing and to anincreased heat resistance of the aluminum alloy.

The aluminum alloy according to the invention has proven to beparticularly advantageous for producing thick-walled components having awall thickness in a range of from 4 millimeters to 30 millimetersinclusive. It is furthermore provided that the casting method used forproducing the component from the aluminum alloy is a diecasting methodor a laminar diecasting method or a sand/permanent mold method. Thealuminum alloy according to the invention is in particular aheat-resistant aluminum alloy, in particular a heat-resistant aluminumcasting alloy, which is particularly advantageously suitable forproducing components for drivetrains.

The invention also includes a method for producing a component from analuminum alloy according to the invention. Advantages and advantageousembodiments of the aluminum alloy according to the invention are to beconsidered advantages and advantageous embodiments of the methodaccording to the invention, and vice versa.

Further advantages, features and details of the invention emerge fromthe following description of preferred embodiments and with reference tothe drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a backscatter electron image (BSE image) ofthe alloy 233 comprising copper (Cu) and molybdenum (Mo) in the heattreatment state T5mod, in which, for example, a component designed as acrankcase and made of the specified alloy is produced by means ofdiecasting;

FIG. 2 schematically shows a BSE image of the alloy 226D (AlSi10Cu3) inthe heat treatment state T5mod, in which a crankcase for example isproduced from the alloy;

FIG. 3 is a BSE image of the alloy 233 comprising Cu and Mo in the heattreatment state T6red;

FIG. 4 is a BSE image of the alloy 226D in the heat treatment stateT6red;

FIG. 5 is a diagram for illustrating mechanical characteristics of thecomponent formed from the respective alloys at room temperature; and

FIG. 6 is a diagram for illustrating mechanical characteristics of thecomponent produced from the respective alloys at 150° C.

DETAILED DESCRIPTION OF THE DRAWINGS

In the drawings, elements that are the same or functionally the same areprovided with the same reference signs.

FIGS. 1 to 4 each show backscatter electron images (BSE images) ofalloys from which the respective components are produced. The alloy isin each case, for example, an aluminum alloy, in particular an aluminumcasting alloy and in this case preferably a heat-resistant aluminumcasting alloy.

The component produced by the respective alloys is in each case, forexample, a component used in a drivetrain of a motor vehicle, thecomponent being, for example, a crankcase, in particular a diecastcrankcase. This means that the component made of the respective alloysis produced by means of casting, in particular diecasting. Inparticular, the component can be a thick-walled component which has awall thickness in a range of from 4 millimeters to 30 millimetersinclusive. By means of the aluminum alloy described in more detail inthe following, particularly advantageous properties, in particularmechanical properties, of the component can be realized. Preferably, thealuminum alloy in each case has the following composition:

8.0 wt. % to 11.0 wt. % silicon,

0.25 wt. % to 4.00 wt. % copper,

0.10 wt. % to 0.50 wt. % magnesium,

0.05 wt. % to 0.60 wt. % manganese,

less than or equal to 0.3 wt. % titanium,

less than or equal to 0.3 wt. % zirconium,

less than or equal to 400 parts per million (ppm) strontium,

at most 1.5 wt. % iron,

at most 1.5 wt. % zinc,

0.001 wt. % to 0.25 wt. % vanadium,

additional additives of 0.01 wt. % to 0.50 wt. % molybdenum,

at most 0.25 wt. % chromium,

at most 0.20 wt. % nickel,

at most 0.15 wt. % cobalt,

and the remainder aluminum, it being possible for impurities oradditional elements to be optionally provided in a proportion of lessthan 0.05 wt. %.

Particularly preferably, the aluminum alloy comprises magnesium at atleast 0.10 wt. % and less than 0.30 wt. %. Alternatively oradditionally, the aluminum alloy preferably comprises manganese at atleast 0.10 wt. % and less than 0.40 wt. %. By reducing the manganeseconcentration, the extensive primary formation ofiron-manganese-containing intermetallic Al₁₅(Fe, Mn)₃Si₂ phases iscounteracted by the aluminum mixed crystals and a rough, block-likeformation of the morphology is avoided. In order to set iron (Fe),however, molybdenum is additionally added, which leads to a polygonalmorphology and a finer distribution of the Fe intermetallic phases. As aresult, the formation of acicular or plate-like β-Al₅FeSi phases issuppressed, which phases would occur when there is a high Fe content anda low Mn content (Mn: manganese). The magnesium content is reduced tothe extent that, as far as possible, the π-Al₈FeMg₃Si₆ phase is notformed. This phase does not dissolve at a solution treatment temperatureof 465° C. and would merely set on account of the increased Fe contentof the additionally alloyed magnesium (Mg) and lead to skeletalFe-containing intermetallic phases which are detrimental to ductility inthe form of a decrease in the elongation at break and no longer providefor strength-increasing precipitate formation.

The copper content (Cu content) is used to adjust the required strengthin a. targeted manner due to the formation of strength-increasingprecipitates during artificial ageing, Nevertheless, it is important tobe aware that a copper proportion that is too high during T5 heattreatment leads to embrittlement. The full strength potential of thecopper in the alloy can be exploited during T6 heat treatment.

The addition of titanium (Ti) brings about grain refinement of thealuminum dendrites. A combination with zirconium (Zr) in an adjustedconcentration can lead to Al₃(Ti, Zr) precipitates which can have astrength-increasing effect. Care should also be taken at this juncturethat titanium and zirconium are not added by alloying in too high aconcentration since this leads to an undesirable formation of Al—Ti—Zrintermetallic phases which reduce ductility. Adding strontium (Sr)brings about an improvement of the Al/Si eutectic system from coarse andplate-like to an improved, coral-like morphology, thus increasingductility. This fine Si morphology can be molded quickly and easily by aT6 solution treatment and the ductility can thus be increased once more.

Production of a component made of an aluminum alloy of this type isdescribed in the following. During production, the above-mentionedaluminum alloy is smelted from master alloys, pure elements or producedby alloying suitable secondary alloys, for example 223 or 226, at asufficiently high temperature. The alloy is furthermore cast into atemperature-controlled, forced-deaerated or vacuum-deaerated permanentmold. If the casting temperature is too low, there exists a danger ofinadequate mold filling and cold running and of undesirable formation ofintermetallic phases, whereas casting temperatures that are too highincrease the danger of porosity, cavitation and hot cracks. Afterremoving the component produced by casting, the component in order torealize the heat treatment state T6red—is cooled in air or—in order torealize the heat treatment state T5mod—is cooled by means of water.

The special characteristic of the microstructure of the componentproduced from the aluminum alloy can be seen with reference to FIGS. 1to 4. FIG. 1 shows a backscatter electron image of the specifiedsecondary alloy 233 comprising copper and molybdenum. Rounded topolygonal molybdenum-containing AlFeMnSi intermetallic phases can beseen. These phases can be found distributed relatively evenly among theAl dendrites in the Al/Si eutectic system since they set concurrentlywith the system. Due to the small size and rounded morphology of thesephases, these increase the ductility of the secondary alloy. The π phaseAl₈FeMg₃Si₆ can be found sporadically and cannot be dissolved by asolution treatment at 465° C. (cf. FIG. 3). By reducing the Mg content,the formation of this brittle phase can be suppressed and the ductilitythus further increased. Potential phases Φ-Al₂Cu and Q-Al₅Cu₂Mg₈Si₆resulting during solidification should be dissolved by a solutiontreatment for three hours at 450° C. (cf. FIG. 3) such that the alloyelements Mg and Cu, which are set into these phases, are provided in theAl mixed crystal for precipitate formation.

FIG. 2 shows a backscatter electron image of the specified secondaryalloy 226D (AlSi10Cu3). On account of the high Fe and Mn content,coarse, block-like intermetallic Al₁₅(Fe, Mn, Cr, Cu)₃Si₂ phases arepresent which, on account of the size thereof, have formed primarily inthe casting chamber of the diecasting machine. This accumulation ofbrittle phases inhibits ductility. Additionally, smaller, polygonalFe-containing intermetallic phases are present which occur only in theactual diecasting mold. In addition to said Fe-containing intermetallicphases, β-Al₅FeSi phases are also present on account of the high Fecontent, which phases appear as needles in the two-dimensionalmicrosection surface and in reality are present as three-dimensionalplates and therefore as extensive, sharp-edged microstructure divisionsbetween the ductile Al dendrites. These phases reduce ductilitysignificantly. On account of the relatively high content of Niimpurities in this secondary alloy, Al₇Cu₂(Fe, Ni) phases are alsoformed which cannot be dissolved by a solution treatment at 465° C. andare therefore furthermore present as brittle phases and additionally setCu (cf. FIG. 4).

While the alloy is setting, formed Al₂Cu, which is not pronounced ineutectic form Al—Al₂Cu—Al₅Cu₂Mg₈Si₆—Si, can be completely dissolved by asolution treatment at 465° C. (cf. FIG. 4), such that, by means of waterquenching, the Al mixed crystal is subsequently saturated in Cu. Theeutectic pockets Al—Al₂Cu—Al₅Cu₂Mg₈Si₆—Si, however, cannot be completelydissolved at 465° C. for three hours. FIGS. 5 and 6 are diagrams forillustrating mechanical properties of components produced from thespecified aluminum alloy. Bars 10 illustrate the 0.2% proof stressR_(p0.2), whereas bars 12 illustrate the yield point R_(m). Triangles 14illustrate the elongation at break A₅.

1.-7. (canceled)
 8. All aluminum alloy, comprising: aluminum; 0.001 wt.% to 0.50 wt. % molybdenum; 0.05 wt. % to 0.45 wt. % magnesium; 0.05 wt.% to 0.60 wt. % manganese; up to 1.5 wt. % iron; 0.25 wt. % to 4.00 wt.% copper; and 0.001 wt. % to 0.25 wt. % vanadium.
 9. The aluminum alloyaccording to claim 8, wherein the manganese is at least 0.10 wt. % andless than 0.40 wt. %.
 10. The aluminum alloy according to claim 8further comprising 8.0 wt. % to 11.0 wt. % silicon.
 11. The aluminumalloy according to claim 8 further comprising: at most 0.3 wt. %titanium; at most 0.3 wt.% zirconium; at most 400 parts per millionstrontium; at most 1.5 wt. % zinc; at most 0.25 wt. % chromium; at most0.20 wt. % nickel; and at most 0.15 wt. % cobalt.
 12. A method,comprising the steps of: producing a component from an aluminum alloyaccording to claim 8 by casting, without pressure or pressurized at aneffective pressure of between 0 bar and 1,000 bar.
 13. The methodaccording to claim 12, wherein the aluminum alloy is cast into a mold ata temperature of 650° C. to 730° C.
 14. The method according to claim12, wherein the aluminum alloy is cast at a temperature of 580° C. to650° C. thixotropically, without pressure or pressurized at an effectivepressure of between 0 bar and 1,000 bar.